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Initial M/C heat-up

or most of us, have installed a mod-con at some point.<BR>Assuming most use a Spirovent or equivalent device for system air-removal, does the system temperature not affect its effectiveness? <BR>What I`m getting-at is, do you guys heat the system-up(once installed), above std. operating temperature to help eliminate the air factor?<BR>If so, how high do you go?<BR><BR>Dave


  • Brad White_203
    Brad White_203 Member Posts: 506
    Magic Numbers

    Hi Dave!

    Temperature and pressure are everything. Typically, it takes at least 140 degrees to release most bulk air at about 8 PSI, (This is from memory, there are charts somewhere that tell you more.) 180F to 200F is much more effective.

    What you are using is Henry's Law, which dictates the amount of gas which can be held in solution in a liquid at specific conditions.

    Naturally the higher the temperature of the liquid and the lower the pressure, the less gas (air in this case) the water can hold.

    It is for this reason that most air eliminators are located at the PONPC and why this is usually coincident with the outlet of the boiler where water is hottest.

    Heating the water at normal operating pressures (say 12 PSI in a one or two storey house) requires higher temperature. If just "filled to the top" but without reserve pressure, the temperature can be less than if under higher pressures.

    As a practical matter, no less than 140F should be used, run for an hour or so, re-vented and topped off. Another round of heating may be required for that last bit of water. If filled to reserve pressure (say 12 PSI or more) then I would use 180F to 200F.

    You can see how actually going to boiling would amplify the gas removal effect. The Spirovent amplifies the removal because it can grab those bubbles out of solution. (They love attention I guess.)

    As a point of reference, I do not usually specify air separators for chilled water systems and just rely on normal venting. I do this because the critical temperatures of air release are never achieved.

    Hey, heads up, Susan the kids and I are going to invade Ottawa in a couple of weeks for Winterlude. Curious, how far are you from Ottawa?
  • Thanks Brad,

    I usually try for 180°(sometimes only 160°) for a few hrs, and I always use a Taco 4900 on the system, of course pumping away from the boiler & the PONPC.

    BTW-Ottawa?, its only about an hour drive from me.

  • Brad White_203
    Brad White_203 Member Posts: 506
    I like the Taco 4900

    although they are a bit chunky. I used an 8-inch size in a 4.5 MBH hot water boiler replacement job and the question was, "OK now, where do we put the boiler?" Sucker was huge and the old system was NOT pumping away. The owner thinks I am a genius. Awww, just doing my job.. :)

    As for the Pall rings, one guy in the office forgot what they called them, remembered it sounded like a saint's name so Googled "Peter rings".. found nothing to do with air removal last we heard from him.. ;)

    I have absolutely no doubt you pipe things correctly- I just mentioned the rationale and how that furthers the objective, for any other readers.

    We are all brushing up on our Canadian English in preparation for our trip. Our 12 year old wants to try out her 7th grade French. If a war starts, it was not my doing, really! And I finally get to spend that 20 Loonie note I have had for too long. Maybe stop at Tom Horton's. We will wave as we go on by.


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